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From:   "Kang, Luwei" <luwei.kang@intel.com>
To:     Alexander Shishkin <alexander.shishkin@linux.intel.com>,
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Subject: RE: [PATCH v13 08/12] KVM: x86: Add Intel PT context switch for
 each vcpu
Thread-Topic: [PATCH v13 08/12] KVM: x86: Add Intel PT context switch for
 each vcpu
Thread-Index: AQHUa3CwucpPcxWRekKi4EsgTEAw/6Utp38AgAFsRVA=
Date:   Thu, 25 Oct 2018 00:06:25 +0000
Message-ID: <82D7661F83C1A047AF7DC287873BF1E172BD64B9@SHSMSX101.ccr.corp.intel.com>
References: <1540368316-12998-1-git-send-email-luwei.kang@intel.com>
 <1540368316-12998-9-git-send-email-luwei.kang@intel.com>
 <87a7n37iuf.fsf@ashishki-desk.ger.corp.intel.com>
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> > +static void pt_guest_enter(struct vcpu_vmx *vmx) {
> > +	if (pt_mode == PT_MODE_SYSTEM)
> > +		return;
> > +
> > +	/* Save host state before VM entry */
> > +	rdmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
> > +
> > +	/*
> > +	 * Set guest state of MSR_IA32_RTIT_CTL MSR (PT will be disabled
> > +	 * on VM entry when it has been disabled in guest before).
> > +	 */
> > +	vmcs_write64(GUEST_IA32_RTIT_CTL, vmx->pt_desc.guest.ctl);
> > +
> > +	if (vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN) {
> > +		wrmsrl(MSR_IA32_RTIT_CTL, 0);
> > +		pt_save_msr(&vmx->pt_desc.host, vmx->pt_desc.addr_range);
> > +		pt_load_msr(&vmx->pt_desc.guest, vmx->pt_desc.addr_range);
> > +	}
> > +}
> 
> From my side this is still a NAK, because [1].
> 
> [1] https://marc.info/?l=kvm&m=153847567226248&w=2
> 

This place is save the host PT status and load the guest PT status before VM-entry when working in Host-Guest mode.

Thanks,
Luwei Kang